Moloney (M)-MSV genome was present in the cell RNA of four cloned revertants derived from M-MSV-transformed S plus L- M-3T3FL cells. However, MSV was not rescuable from these clones by MuLV, nor inducible by 5-iododeoxyuridine. Clones of SC-1 cells were isolated following transformation by MSV-Z. They were characterized as S plus L- cells, and the RNA from these cells hybridized with the complementary DNA from M-MSV. BIBLIOGRAPHIC REFERENCES: Nomura, S., Fischinger, P. J., Hartley, J. W. and Mattern, C. F. T.: Induction of a novel transforming virus (MSV-Z) from sarcoma positive leukemia negative 3T3FL mouse cells. Virology 69: 635-646, 1976. Nomura, S. and Fischinger, P. J.: Rapid screening assay for revertants of MSV-transformed cells. In Prescott, D. M. (Ed.): Methods in Cell Biology. New York, Academic Press, Inc., 1976, Vol. 14, pp. 229-236.